20 TOPOGRAPHICAL ANATOMY OF THE 



— by which it is partly overlapped — and appears to be the direct 

 continuation of the longissimus dorsi. It arises from the transverse 

 processes of the first six or seven thoracic vertebrre, and ends on the 

 transverse processes of the last four cervical vertebnc 



M. SCALENUS. — The brachial plexus of nerves divides the scalene ^ 

 muscle of the horse into two parts. The dorsal and smaller portion of 

 the muscle is attached to the cranial border of the first rib close to its 

 vertebral end, and to the transverse process of the last cervical vertebra. 

 The larger, ventral portion arises from the rough area on the cranial 

 border and outer surface of the first rib proximal to a smooth groove 

 produced by the subclavian vessels, and is inserted to the transverse 

 processes of the sixth, fifth and fourth cervical vertebra^. 



N. CERVICALIS SECUXDUS. — The present is a convenient time at 

 which to examine the ventral branch of the second cervical nerve. The 

 nerve appears at the lateral border of the caudal oblique muscle of the 

 head. Underneath the brachio-cephalic muscle it communicates by 

 anastomotic branches with the accessory nerve and with the ventral 

 branches of the first and third cervical nerves, and is concerned in the 

 formation of the nerve that has been noted as supplying the sterno- 

 thyro-hyoid muscle. It then emerges between the two parts of the 

 brachio-cephalic muscle and immediately divides into two branches. 



(1) The great aiiTicidav nerve (n. auricularis magnus) follows 

 the edge of the wing of the atlas and the contiguous border of the 

 parotid gland, and ends in the skin covering the convex surface of the 

 external ear. 



(2) The cutaneous cervical nerve (n. cutaneus colli) is connected 

 with the ramus colli of the seventh cerebral nerve, and the combined 

 nerve has already been found in association with the jugular vein. As 

 has also been noted, a part of the cutaneous cervical nerve passes into 

 the space between the two halves of the mandible. 



M. LONGISSIMUS CAPITIS. M. LONGISSIMUS ATLANTIS. — These twO 



muscles are readily distinguished, but it is convenient to consider them 



together. They are long and narrow, extending the whole length of 



the neck, and lie medial to the spleuius and longissimus cervicis. They 



arise in common from the transverse processes of the first two thoracic 



vertebrse by aponeurotic tendinous bands that are connected with the 



underlying semispinalis capitis muscle, and receive additional bundles 



of fibres from the articular processes of the last five (or six) cervical 



vertebrse. 



^ Scalenus [h.],' <rKa\rjv6s (scalenos) [Gr.], uneven. The outline of the muscle is a 

 triangle with unequal sides. 



